am I do something wrong, just moving geo around the scene cause Max to hang up for 30 seconds, I assume it the corona map distance always calculating causing this. There should be some kind of global check box to only calculate at render time or scenes can become unusable.

After running a few test this absolutely is the case. I can understand why a person would want to have it calculate all of the time for propagating trees in scatter, or using as a physical displacement, but if you are using Corona distance map to blend materials and have several in your scene, it brings scene speed down to a crawl. This needs to be addressed, there should be some sort of global override that only calculates this at render time.

Hi, can you send us a scene (even very simple) where this can be observed, and instructions how to reproduce it? (just hit render? or start IR?)You can use this uploader and let us know here what was the file name: https://corona-renderer.com/upload

Yeah, that would be a solution. The more objects distance map has to consider the slower it gets, a checkbox for rendertime only would be great, but instead of a global setting, it should be set per distance map.

Is the lag you get present while rendering with IR only? I've learnt the hard way to avoid doing any changes to the map or the distance objects while IR is running, it's either unstable or locks up Max for a... while.

I am talking about view port lag. I feel like this shader is ramming out my video card, anyone confirm where this map is being stored, because I know I can create real time displacements in the viewport from it, so it so it is either resident in ram, or the video card's ram.

That happens usually if you have many objects added to a distance map or have multiple maps and you move any of these or edit them in some way. If the material editor is open and displays a map or material using these maps it gets a lot worse, closing it may help. Collapsing these objects so the object list to update is shorter helps too. Not feasible in many situations, though.